View Compilation Error

0_0_23257315_24419.cpp: In member function 'void HUGE_INT::Display()':
0_0_23257315_24419.cpp:38:22: error: 'strlen' was not declared in this scope
     n=(int)strlen(num);
                      ^
0_0_23257315_24419.cpp: In constructor 'HUGE_INT::HUGE_INT(char*)':
0_0_23257315_24419.cpp:46:26: error: 'strlen' was not declared in this scope
     int len=(int)strlen(n);
                          ^
0_0_23257315_24419.cpp: In function 'int operator>(HUGE_INT, HUGE_INT)':
0_0_23257315_24419.cpp:87:27: error: 'strlen' was not declared in this scope
     len1=(int)strlen(m.num);
                           ^
0_0_23257315_24419.cpp: In member function 'HUGE_INT HUGE_INT::operator*(HUGE_INT)':
0_0_23257315_24419.cpp:155:28: error: 'strlen' was not declared in this scope
     int x = (int)strlen(num);
                            ^
0_0_23257315_24419.cpp: In member function 'HUGE_INT HUGE_INT::operator/(HUGE_INT)':
0_0_23257315_24419.cpp:190:30: error: 'strlen' was not declared in this scope
     len1=(int)strlen(self.num);
                              ^